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WOLF BLITZER, CNN ANCHOR: Happening now, breaking news, terror investigation. Chilling new information about the deadliest mass shooting in U.S. history. We're learning more about the gunman, his victims and the horror that happened inside that Orlando nightclub.

Missed signals. The FBI reveals they previously investigated the killer, even placed him on terror watch lists. A former co-worker describes him as an angry, violent bigot. But his weapons purchase and attempt to buy body armor failed to trigger alarms. How did he fall through the cracks?

Horror and heroism. New details about the massacre inside the club. Some victims reaching out to loved ones during the hours'-long nightmare and pleading for help. Others risking their own lives to save their friends. Did key decisions by police prevent an even greater loss of life?

And vastly different views. The presidential candidates respond to the Orlando killings by outlining very competing visions of America. Hillary Clinton calling for a ban on assault-style weapons while Donald Trump restates his call for a ban on Muslims entering the United States. How will voters respond?

I'm Wolf Blitzer. You're in THE SITUATION ROOM.

ANNOUNCER: This is CNN breaking news.

BLITZER: We're following the breaking news, disturbing new information about the terror attack on that gay nightclub in Orlando by a gunman who pledged allegiance to ISIS.

We're now learning that American-born Omar Mateen was the subject of a ten-month investigation by the FBI. He was interviewed by agents three times, including after he expressed sympathy for a suicide bomber and was even placed on two terror watch lists, but the interviews were deemed inconclusive, and the investigation was eventually dropped.

And there's chilling new video of the massacre tonight. A snapshot Snapchat recorded by a victim as the gunfire was breaking out. The 25-year-old woman was one of the 49 people killed in the attack.

We're covering all angles of the breaking news this hour with our guests, including the chairman of the House Homeland Security Committee and the Senate Intelligence Committee. And our correspondents are at key locations, including the nightclub and the killer's home. They're talking to their sources. Our expert analysts are also standing by.

Up first, the latest on the investigation. Our chief national security correspondent, Jim Sciutto, is in Orlando for us. Jim, what are you hearing?

JIM SCIUTTO, CNN CHIEF NATIONAL SECURITY CORRESPONDENT: Wolf, tonight investigators say this was an act of terror, but not one that was directed by a terror group outside the country.

However, we do know the shooter did express allegiance to ISIS on the night of the attack; and in the past he'd expressed allegiance to other terror groups, been in touch with at least one known terrorist, enough to prompt that FBI investigation you mentioned launched in 2013. The investigation ended after ten months in 2014, and some two years later the violence we saw carried out just behind me here at the Pulse nightclub.

(BEGIN VIDEOTAPE)

SCIUTTO (voice-over): This is the moment Pulse nightclub turned from celebration to terror.

(GUNFIRE)

SCIUTTO: Gunfire caught on video as 25-year-old Amanda Alvear chatted online with a friend. She did not survive. Tonight, U.S. officials are calling the deadliest shooting in American history an act of terrorism, though there is no evidence the shooter, Omar Mateen, had contact with ISIS or other terror groups.

BARACK OBAMA, PRESIDENT OF THE UNITED STATES: As far as we can tell right now, this is certainly an example of the kind of home-grown extremism that all of us have been so concerned about for a very long time.

SCIUTTO: But today, the FBI director, James Comey, said the bureau investigated Mateen for ten months in 2013 and placed him on two terror watch lists, though he was removed when the case ended. He was still able to buy two guns legally in the last two weeks.

JAMES COMEY, FBI DIRECTOR: We're working to understand what role anti-gay bigotry may have played a motive in this attack. Again, it's early. We're working hard to understand the killer and his motives and his sources of inspiration.

SCIUTTO: Just after 2 a.m. Sunday morning, as Pulse nightclub readies for closing, Omar Mateen sprays a barrage of bullets into a crowd of some 300 people. Witnesses believed the initial gunfire is part of the music.

UNIDENTIFIED MALE: I was just dancing to music and you hear a bang, bang and it's not even -- I don't know, 150 feet in front of you. Literally, there's people being shot down.

SCIUTTO: An off-duty police officer working at the front entrance of the club engages in a gun battle, firing several rounds at the shooter.

Additional officers then respond and engage Mateen in another fire fight, forcing him to retreat to the bathroom, where officials say he held several hostages.

Around 2:30 a.m., Mateen calls 911 from the bathroom three times, pledging his allegiance to ISIS, other terror groups and expressing support for the Boston bombers and Abu-Salha, the American suicide bomber who killed himself in Syria.

COMEY: There were three different calls. He called and he hung up. He called again and spoke briefly with the dispatcher and then he hung up. And then the dispatcher called him back again, and they spoke briefly. So there were three total calls.

CHIEF JOHN MINA, ORLANDO POLICE: He was cool and calm when he -- when he was making those phone calls to us.

SCIUTTO: At 5 a.m., a full three hours later, a SWAT team uses an explosive device and an armored vehicle to break through the wall of a different bathroom, rescuing dozens more.

UNIDENTIFIED MALE: That was a breach. That was a breach.

SCIUTTO: Mateen emerges from the same hole in the wall, armed with a handgun and long gun, firing at officers who then killed him.

(END VIDEOTAPE)

SCIUTTO: Another line of investigation, his foreign travel. We learned today that he traveled twice to Saudi Arabia in 2011, 2012. That for a Muslim pilgrimage. He also traveled to the UAA [SIC] -- UAE, United Arab Emirates. No indication as of yet that he met with any bad actors' terror groups, but they are still exploring the possibility.

And Wolf, one reason the FBI ended this was investigation was his confusion -- confusing expressions of support, not only for a group like ISIS but al Qaeda groups, Hezbollah, groups with competing messages that are fighting themselves.

It's one reason they did not take him seriously at that time. It's possible that there were multiple motivations behind this shooting, Wolf. And that is something investigators are still looking into.

BLITZER: Yes. By all accounts, this investigation only just beginning. Jim Sciutto, thanks very much.

We're also learning more information about the shooter, the 29-year- old Omar Mateen. Brian Todd is in Fort Pierce, Florida, where he had been living, Matten.

Brian, you've been watching the intense investigation going on at the killer's apartment. What are you learning?

BRIAN TODD, CNN CORRESPONDENT: Wolf, this is his apartment building where Omar Mateen lived here in Fort Pierce. Police and evidence specialists have been coming in and out of here all day, collecting crucial materials, sealing off that apartment from the media.

Meanwhile tonight, we're getting new and very chilling information about this mass killer and the instances when he came to the attention of federal law enforcement.

(BEGIN VIDEOTAPE)

TODD (voice-over): Tonight, a portrait of a mass killer with a deadly mixture of hate and radicalization.

COMEY: We are highly confident that this killer was radicalized and at least, in some part, through the Internet.

TODD: FBI director James Comey says the FBI first became aware of Omar Mateen in 2013 following reports of threats and inflammatory statements. And from that time to the night of the massacre, Mateen gave vague and conflicting indications of allegiances to terrorist groups.

COMEY: First he claimed family relations to al Qaeda. He also said he was a member of Hezbollah, which is a Shia terrorist organization that is a bitter enemy of the so-called Islamic State, ISIL. He said he hoped that law enforcement would raid his apartment and assault his wife and child so that he could martyr himself.

TODD: The FBI tracked Mateen, looking for terrorist connections, for ten months before closing that case. Questions tonight whether Mateen should have been tracked more closely.

COMEY: We're also going to look hard at our work to see whether there was something we should have done differently. So far, the honest answer is, I don't think so. I don't see anything in reviewing our work that our agents should have done differently.

TODD: Mateen was born in New York, the son of Afghan immigrants. He worked for nine years as a security officer at G4S security, one of the world's largest private security companies. Investigators are looking into what led him to this horrible act, but all indications suggest preparation and premeditation for a mass killing.

The manager here says they don't sell body armor of any kind, and Mateen was out the door in about five minutes. But a U.S. official briefed on the investigation tells CNN that suggests to investigators that Mateen might have been planning the attack for some time.

UNIDENTIFIED MALE: You don't know why he did what he did?

SEDDIQUE MATEEN, FATHER OF OMAR MAHEEN: I'm not aware at all. I wish -- I wish he was alive so I could ask him the same question that you have. And I cannot -- I cannot tell you why he did do such an act. This is against the principle of me and the whole family.

TODD: Though his father gave no concrete answers as to why, others who knew Mateen described him as unhinged, homophobic and racist. His ex-wife described a brief but violent relationship to a mentally ill man whom she was only able to escape from through her family's help.

SITORA YUSUFI, MATEEN'S EX-WIFE: There was definitely moments that he expressed his intolerance to homosexuals. This was a sick person that was really confused. And went crazy.

TODD: This man says he worked with Mateen as a security guard.

DANIEL GILROY, FORMER CO-WORKER OF MATEEN: He said, "I hate all those 'N's,' and I wish I could just kill them all.

TODD: Daniel Gilroy's claims could not be independently verified, but he says he was so upset that he requested to be transferred and eventually quit the security company where they worked together.

GILROY: I saw it coming. I mean, everything. He told me he was going to do it. Besides the date and the location, he said he was going to kill a whole bunch of people.

(END VIDEOTAPE)

TODD: Daniel Gilroy says he told their employer, G4S Secure Solutions, several times about Omar Mateen's behavior, but he says the company didn't do anything.

Now, a company official with knowledge of the situation tells CNN that G4S was not aware of any other complaints from other employees, including Daniel Gilroy's claims.

And we have to say, Wolf, people were upset that Omar Mateen went through two very rigorous security checks, background checks when he was employed at G4S, once when he was hired in 2007, once in 2013. Both included psychological screening -- Wolf.

BLITZER: What can you share with us right now? What's the latest you're learning?

MCCAUL: Well, I think the latest that has come out, he traveled to Saudi Arabia, to Mecca in both 2011 and 2012. he gets on the radar of the FBI in 2013.

You heard the employer -- employee talk about how he saw this coming. There are a lot of unanswered questions about these investigations that took place. Another one in 2014 where there were connections at his mosque with probably the most dangerous suicide bomber in Syria.

BLITZER: An American, a Floridian.

MCCAUL: He traveled from Florida into Syria and a truck bomb in one of the most deadly suicide bombing operations in Syria.

So there are a lot of flags in this case. We're going to be taking a look at that in Congress in terms of what we could have done, what maybe we could do differently to stop this from happening in the future.

BLITZER: Do you know how long he spent in Saudi Arabia, with whom he met there?

MCCAUL: In 2011, he was there for eight days, in 2012, ten. We don't know who he met with. I would hope when the FBI opened their investigation, they looked into these -- the travel that he had and the people he met with.

BLITZER: Did someone in the FBI drop the ball?

MCCAUL: I don't want to jump to that conclusion right now. You know, as you know, I spearheaded the Boston bombing oversight. You know, the FBI has a tremendous burden on them right now. They have tens and thousands of these leads that come in every year. There are thousands of investigations in all 50 states.

I trust James Comey. He's going to lead a briefing tomorrow before the House and the Congress with both Comey, Secretary Johnson and the NCTC director, Mr. Rasmussen.

BLITZER: National Counterterrorism Center.

I asked the question because they interviewed this guy. He was on FBI surveillance for ten months, and they then said the information was inconclusive.

This isn't the first time a terrorist here in the United States was investigated and cleared and then went on to kill and to massacre people. Major Nidal Hasan at Fort Hood, Texas, he was investigated. They looked at his communications with Anwar al-Awlaki, one of the al Qaeda masterminds. He was cleared and went on to kill all those fellow soldiers.

Tamerlan Tsarnaev, one of the Boston Marathon massacre terrorists, he was investigated. He was cleared. There seems to be a pattern here. MCCAUL: Well, there does, whether it was the Boston bombing with

Tamerlan and, of course, that case was closed. And Nidal Hasan, that case was closed. And then we saw Chattanooga happened and now this. The cases closed.

I don't want to draw a complete similarity to Boston. I think some major mistakes were made there. But we will be proving our oversight responsibility to look at this case and find out what went wrong.

In every one of these cases, though, Wolf, you see in the radicalization process flags going up, and those flags are missed along the way. If we could catch those flags beforehand, we could stop an act of terrorism.

BLITZER: They've got to really do a major postmortem now, review what happened, learn lessons to make sure it doesn't happen again. I'm sure, as you're involved in the oversight, the Department of Homeland Security, you'll be doing that, as well.

We heard very conflicting -- different speeches today from Hillary Clinton and Donald Trump. Hillary Clinton, she called for reviving the ban on assault weapons. Donald Trump doubled down in his call for banning Muslims from coming to the United States. Who's right?

[17:15:08] MCCAUL: Well, this is presidential politics. A major tragedy occurred. We're in the grieving process. The bodies haven't been buried yet. And to see this now consumed with presidential politics, I think in some ways is regretful.

Having said that, addressing those issues, I do think Mr. Trump is correct that we need to look at the vetting process from high-threat areas. And we need to find a way, like we did under the SAFE Act with the Syrian refugees to ramp up that vetting process, put a pause on the program and make sure we don't have threats coming into the United States that can attack the homeland.

This is the fourth major attack since -- fifth since 9/11. The tempo is increasing, not decreasing. And I'm very concerned about the threat environment right here in the United States.

BLITZER: The fact that this guy could get an assault weapon, this AR- 15, that's pretty worrisome.

MCCAUL: Well, it's legal. And the federal courts have ruled that this is a legal firearm under the law. It has not gone to the U.S. Supreme Court. I would think after this case, that it probably will.

BLITZER: Mr. Chairman, thanks for coming in.

MCCAUL: Thanks, Wolf.

BLITZER: Mike McCaul, chairman of the Homeland Security Committee.

Take a look at this live picture coming in from Paris right now. The Eiffel Tower lit up in tribute to the Orlando victims. We see that there. Let's pause for one second and just watch. Coming up, I'll ask the chairman...

(COMMERCIAL BREAK)

[17:26:06] BLITZER: We're following the breaking news in Orlando. The terror attack, the FBI now revealing the gunman was previously investigated and placed on not one but two terror watch lists, eventually removed from those lists when the case was dropped.

Let's dig deeper with the chairman of the Senate Intelligence Committee, Republican Senator Richard Burr of North Carolina.

Senator, thanks very much for coming in. Have you been briefed on this terrorist's movements in the days leading up to this attack?

SEN. RICHARD BURR (R-NC), CHAIRMAN, SENATE INTELLIGENCE COMMITTEE: Not on the days leading up.

Listen, you and I have talked before that there are many places in the United States that were targets. This is not the first time. The city of Orlando, it has come up, but there are many more places around the world, especially in Europe. And this is the new norm.

ISIL has really, through social media, not only recruited fighters, but they now recruit terrorists to carry out acts. So it's one seamless operation for them.

BLITZER: You see this as a direct link between is, not al-Nusra, not Hezbollah, some other terrorist group he may have once pledged allegiance to, but ISIS specifically?

BURR: Well, this individual has claimed allegiance in the past to a number of different groups. And that's what led the FBI to realize that he really wasn't a threat when they did some interviewing.

But of late, ISIL is the one that is actively out on social media trying to radicalize people to this point.

BLITZER: And he was recruited that way through social media. There are these reports he was also casing out Disney World in Orlando. What, if anything, can you tell us about that?

BURR: I'm not sure that we know the full extent, but the attack was clearly planned. He had -- he had done some surveillance of this location. So it's very possible that he was looking for other locations in Orlando, as well, and chose this.

BLITZER: When you say he was looking, he had cased this gay nightclub. He had been there, went inside before? Is there video of him going in and out on earlier occasions?

BURR: I'm not sure of the extent that they have, but there's certainly an indication that he was familiar with where he was going.

BLITZER: Is that the testimony of people who were there, that they knew this guy from earlier visits? BURR: No. I think -- I think some of this, Wolf, is the

preliminaries of going through some of his electronics and some interviews with people to be recognized.

BLITZER: So how concerned do Americans need to be right now that there could be additional terror attacks like this one in the works?

BURR: Oh, I think I've said for the last 12 months to you, it was a matter of time. We never know, from the cities that we have specific threats in, whether there's an individual or a cell that's there.

The clearer thing is there is an intent and capability. As long as you have intent and capability, and you have no strategic change on the part of the United States to go overseas and to take on ISIL and to eliminate the safe haven, to put out these social media blitzes that they do. We now have ISIL in 17 different countries. They're no longer Syria and Iraq. And now we have to spread our defensive mechanism out in a much larger geographical footprint.

BLITZER: What have you learned about his two visits to Saudi Arabia?

BURR: It seems that both of them were as -- it was to Mecca. It was a pilgrimage. But maybe over time, we'll find the connection. But this seems like an individual that, over the last several years, became radicalized.

BLITZER: What about the United Arab Emirates? I take it he was there, as well.

BURR: I have no information on the UAE.

BLITZER: He went there and he went twice to Saudi Arabia. Did the FBI drop the ball?

BURR: No.

BLITZER: Why do you say that?

BURR: I say it because these are very seasoned interviewers, and they went with the information that was shared by his co-workers. And over a nine-month period, they asked a lot of questions. The FBI is not going to let somebody go that they've got a concern with.

Let me say this. Anybody that's interviewed, anybody who goes through this process is automatically on the watch list.

BLITZER: There wasn't enough on the watch list to prevent him from buying an AR-15 semi-assault weapon that killed a lot of people.

BURR: You're exactly right. He was a U.S. citizen, and he hadn't been accused of any crime. One of the responsibilities we have is to make sure that individuals in this country have their rights and that they're not taken away.

Now, that's a debate we may have, as to whether there's a new threshold. But this was an individual that was interviewed over nine months by the FBI, and one day he was a Sunni; and the next day he was a Shia.

BLITZER: He wanted to go and buy body armor, as well. More sophisticated, tougher body armor than police usually have. Shouldn't that have raised some alarm bells?

BURR: Well, I'm not sure that anybody really knew that at the time. But...

BLITZER: The store where he wanted to buy it, they didn't sell it to him, but they discovered that he wanted to buy that type of body armor. Is there some procedure that should be in place, that the store should notify the local authorities, say, "Some guy wanted to buy some pretty advanced body armor"?

BURR: Director Comey said today, if you see something, say something. And that's still a very crucial component of the defense that we've got in this country. Whether you're in New York or whether you're Orlando, you see something out of the ordinary, report it to authorities.

BLITZER: Mr. Chairman, thanks for coming in.

BURR: Thanks, Wolf.

BLITZER: Richard Burr is the chairman of the Senate Intelligence Committee.

Coming up, amid the horror, acts of heroism. Survivors of the nightclub massacre speaking out. More on the breaking news. That's next.

(COMMERCIAL BREAK)

BLITZER: We continue following the breaking news coming in from the investigation into the Orlando nightclub massacre.

[17:31:09] The FBI now says about a half hour into the three-hour siege, the gunman called 911 twice, took one phone call from the 911 dispatcher.

Also, we don't want to lose sight of the heroism and the sacrifice of the people inside the club, those who survived and those who did not.

Let's go back to Orlando. CNN anchor John Berman is standing by.

John, there were so many acts of bravery we're learning about. Share with our viewers.

JOHN BERMAN, CNN ANCHOR: Wolf, there were more than 300 people in the Pulse nightclub behind me. Three hundred people. It was packed. That means 300 stories. Brave, courageous and also wrenching.

(BEGIN VIDEOTAPE)

BERMAN (voice-over); A loud, packed joyous night inside the Pulse nightclub. This chilling new video, a Snapchat from 25-year-old Amanda Alvear, shows the final carefree moments inside Latin night as last call approaches. You hear the first moments of gunfire.

(GUNFIRE)

BERMAN: Amanda Alvear does not survive.

Armed with an AR-15-style rifle and a handgun, the shooter begins his rampage, but inside not everyone knows what is going on.

CHRISTOPHER HANSON, SURVIVOR: It went with the beat almost until you heard too many shots. It was like bang, bang, bang.

BERMAN: Officers rushed to the scene, trading fire with the shooter. Moments later, an urgent message from the club on Facebook: "Everyone get out of Pulse and keep running."

Gunshots continued to ring. Panic spreads in the darkness, even as the loud music roars. Then, moments of heroism and horror. One witness says he just saw bodies going down just one after another after another.

HANSON: I was having a drink at the bar. I fell down. I called out. People were trying to escape out the back.

BERMAN: Christopher Hanson escapes unharmed but then goes back to help others.

HANSON: I took my bandana off and put it in a knot, and I shoved it in this hole, the bullet hole that was in his back. It didn't go through. It stayed in. Then the second person I helped, she got hit in the arm.

BERMAN: The gunman retreats to a bathroom in the back of the club and takes hostages.

Thirty-year-old Eddie Justice, an accountant from Orlando, hides in the bathroom and sends this message to his mother.

Son: "Trapped in the bathroom."

Mom: "What club?"

Son: "Pulse."

Son: "Call police. I am going to die."

Mom: "I'm calling."

Moments later...

Son: "I am still in the bathroom. He is coming. I am going to die."

His mother tries to call him but no answer. Eddie Justice does not survive.

A three-hour standoff takes place with 100 officers outside the club, while in the bathroom the gunman calls 911 but hangs up. He calls back and speaks briefly with the dispatcher and then hangs up again. The dispatcher calls back, and the shooter states he's doing this for the leader of ISIS.

Finally, at 5 a.m., a SWAT team blows a hole in the outer wall. An armed vehicle plows in. They engage the gunman and kill him. Many hostages are rescued. The immediate ordeal is over.

One of the bartenders is hiding under the glass bar. Police inside ask, "If you are alive, raise your hand." The bartender and other survivors are brought out. Many are not. Too many.

(END VIDEOTAPE)

BERMAN: Forty-nine people killed and that many more injured. That means a full one-third of the people inside that nightclub killed or wounded. Wolf, 29 remain in the hospital tonight. Five are said to be in grave condition. Their story continues. Their fight very much goes on -- Wolf.

BLITZER: John Berman reporting, thank you.

Joining us now in THE SITUATION ROOM, our national security analyst, Peter Bergen, whose latest book, "United States of Jihad," is about the home-grown terror threat.

Tom -- actually, hold on for a moment. Everyone hold on for a moment. I want to take a quick break. We're getting some more information. I'm going to get that information out. We'll take a quick break. We'll be right back.

(COMMERCIAL BREAK)

[17:40:05] BLITZER: The FBI today revealed new details about the gunman who killed 49 people and wounded 53 others at that Orlando nightclub. We're back with our counterterrorism and national security experts.

Tom Fuentes, Director Comey said they introduced confidential sources while interviewing the gunman. They followed the gunman. There was a ten-month-long investigation. He said the investigation proved to be inconclusive. Yet, he was successfully able to carry out the deadliest shooting in U.S. modern-day history. What did the FBI miss?

TOM FUENTES, CNN SENIOR LAW ENFORCEMENT ANALYST: Well, what they missed is that they couldn't predict what this guy would do three years later after that case. That investigation was in 2013. And apparently, he was just not ready to initiate his attack and didn't show any indications that he was about to initiate an attack, even with all of that extensive investigation. That's the problem in these cases. The FBI, even with an extensive

investigation, cannot read the mind of one individual. Now, if the individual communicates with others and they do a plan together, it's much easier for that to be leaked out among -- the FBI to become aware of it.

But in that case, he hadn't done it yet. And we know in modern cases of radicalization, the bureau refers to that as the period of time flash to bang. In other words, a time that a person radicalizes until they actually do the attack. It used to be six months to a year. Now it's a matter of days or weeks, and we've seen that in this case. It's only within the last week that he bought the two firearms used in this case and then recently the attempt to buy body armor.

So that's what the difference is here. The investigation was at a time when he was not ready to initiate the attack, so they saw no indication that he was and can't sustain that forever.

BLITZER: Yes. They did a second round of questioning him in 2014, as well. That came out inconclusive.

You know, Phil, the FBI director Comey said -- and I'm quoting him now -- he said we are looking for needles in a nationwide haystack. How does the FBI not have a way to track those even after an investigation is closed, even when someone wants to buy that kind of body armor that's really, really sophisticated?

PHIL MUDD, CNN COUNTERTERRORISM ANALYST: Well, there's a couple questions to answer, Wolf. The first is, there is a trigger here, but the FBI can't look at that trigger. That is a closed investigation. This individual goes to buy body armor or a weapon, that weapons check, as you know, doesn't go through and determine whether this fellow was investigated three years ago.

But the second and more difficult question, which we haven't talked about is we're looking at this case in isolation. Every day, the FBI is looking at all those kids, the young men and young women that have gone over to Syria to fight. Some hundred plus have come back to the United States. Some of those individuals are communicating with ISIS via Twitter. Some are communicating, possibly, with ISIS and al Qaeda in Yemen.

In the midst of cases like that, Wolf, somebody walks in, friends, family, in this case a co-worker and says, "I'm worried about somebody I know." This is a prioritization process and when you're dealing with thousands of cases simultaneously, sometimes prioritization is not going to work, Wolf.

BLITZER: Mike Rogers, should there be a full-scale review now of lessons learned, for example, of what was missed, did someone drop the ball, in order to make sure that it doesn't happen again?

MIKE ROGERS, CNN COUNTERTERRORISM ANALYST: Well, every case like this should be reviewed. I think there's a couple of...

BLITZER: Did someone drop the ball here? ROGERS: I'm not sure that they did. Although think about it. If the FBI director -- and I assume he is right -- introduced confidential informants to this case, that's a pretty high level. That's a pretty...

BLITZER: Explain what that means.

ROGERS: That means that they introduced somebody that was cooperative with the FBI into -- into his daily life to ask questions, to get close to him, to try to determine are you, in fact, trying to -- are up to something? Are you, in fact, planning a terrorist attack. Are you trying to...

BLITZER: Because if it was some sort of a sting operation...

ROGERS: Absolutely. And that's what that means when the FBI director says it. That's a very high-level investigation they're introducing. That means it's time consuming. They've spent a lot of time doing it.

Interestingly, Senator Burr brought this up today, that during the course of those interviews, think of the impossible job for the FBI. He said that he was -- would fight on behalf of Hezbollah. And in subsequent interviews, he said he would fight on behalf of al Qaeda. In subsequent interviews, he apparently said he would fight on behalf of ISIS.

He's covered every team on the field. And what the FBI is probably making a determination is, he sounds more candidly a little offbeat than he does a committed jihadist.

And so, given what Phil Mudd talked about is the severity and the number of cases coming over the transom at the FBI, they did a pretty thorough investigation but couldn't conclusively say he was working with somebody known to be a terrorist and planning operations; couldn't determine that he was buying weapons at that time in operations.

[17:45:00] All of that will be reviewed and should be reviewed, because maybe something in that case showed that there should be some notification on weapons purchase. There should be some notification on watch lists that would keep him on there longer than he was.

BLITZER: He also apparently was watching Anwar al-Awlaki videos on the Internet and whether he pledging allegiance to ISIS or al-Nusra, an affiliate of al Qaeda, or Hezbollah, all these groups, they may be Shia, they may be Sunni, but they have something very much in common, the hatred of the United States, right?

PETER BERGEN, CNN NATIONAL SECURITY ANALYST: Indeed. And we saw the San Bernardino, the husband, shopping around. He was interested in al Qaeda, then Shabaab, and finally ISIS. And so, you know, part of this, ISIS didn't exist until 2014, so, you know, the FBI first investigated in 2013 so, you know, this guy was shopping, sort of the jihad organization of the day and you just mentioned what they are.

BLITZER: All right. Guys, stand by because there's more information coming in as well. We'll have more on the unsolved mysteries related to the Orlando shootings.

Back in 2007, the killer was expelled from a law enforcement training academy and fired from Florida's corrections department. But not before getting extensive training in firearms. We're learning much more. Stay with us.

(COMMERCIAL BREAK)

[17:50:37] BLITZER: We continue to follow the breaking details in the investigation of the mass shooting at the Orlando nightclub. The city's mayor says 48 of the 49 people killed now have been identified and their families are being notified.

Joining us now from Orlando is Chad Griffin. He's the president of the Human Rights Campaign, the largest LGBT civil rights organization in the country.

Chad, thanks very much for joining us. What does it mean that this attack came during Gay Pride Month?

CHAD GRIFFIN, PRESIDENT, HUMAN RIGHTS CAMPAIGN: You know, Wolf, I have to say this tragedy has really struck this community unlike perhaps any other in our history. We have faced this moment before, but never of this magnitude. And you know, Pride month, it was born out of protest and celebration. It was a time when we had to take to the streets and to fight for our rights, when our opponents wanted to keep us in the closet.

And it is interesting the parallels that this is happening in this month and that this tragedy happened during the month of Pride because that club right behind me was so much more than a club, it was a place of solitude. It was a place where LGBT people, particularly young people, so many of them in their early 20s, could come and that was their safe place, their safe place to organize and to celebrate.

And it might have just been the one place for so many of them where they could be their true and honest selves, and to think that that one place ended up where they took their last breath is something that is -- that is unconscionable.

BLITZER: Have you had a chance, Chad, to speak with some of the survivors and other family members?

GRIFFIN: We haven't yet, Wolf. I arrived here a few hours ago. You know, we have nearly 300,000 members and supporters here in the state including tens of thousands here in Orlando. And that nightclub is a place that we have held so many events. It's been a gathering place for our own organization. We know that we have members and supporters that were in the nightclub and were impacted that night. So I've had a few hours and have spent time with our local leaders and with the local community expressing our deepest sympathies and asking what more can we do.

BLITZER: Donald Trump spoke out about the attacks today. I want to play a little clip for you and get your reaction, Chad. Listen to this. (BEGIN VIDEO CLIP)

DONALD TRUMP (R), PRESUMPTIVE PRESIDENTIAL NOMINEE: Ask yourself who is really the friend of women and the LGBT community? Donald Trump with actions or Hillary Clinton with her words?

I will tell you who the better friend is, and someday I believe that will be proven out big league.

(CHEERS AND APPLAUSE)

TRUMP: And by the way, the LBGT community is just -- what's happened to them is just so sad and to be thinking about where their policies are currently with this administration is a disgrace to that community.

(END VIDEO CLIP)

BLITZER: All right. I want you to react to that, Chad.

GRIFFIN: Well, Wolf, at a time like this no person in America, regardless of their political beliefs, should be using a tragic moment like this for their own personal ambition and their political desires, and I, and I think the broader community and Republicans and Democrats alike, were disgusted by what we saw Donald Trump do today.

And I want to say two things about what he said. First and foremost, he is no friend to the LGBT community. He is no friend. And at a moment like this when a leader should put their personal ambitions and their partisan differences aside or just shut up, but if they choose to speak out, they should be speaking from a place of unity and a place of sympathy, and of talking about building bridges.

And I would tell you, Wolf, I bet there's not a single family member or friend or brother or sister or girlfriend or boyfriend that is suffering from this great loss that's found any comfort in what Donald Trump had to say today. Instead he was up there bragging about the fact that he claims he predicted this.

And let me say one other thing. LGBTQ people, we are Muslims, we are women, we are Latinos.

[17:55:04] We are as diverse as the fabric of this nation, and Wolf, any attack on any one of us is an attack on all of us. And it's shameful and disgusting what Donald Trump did today and what he said today. And I hope he says not another word about it.

BLITZER: Chad Griffin is the president of the Human Rights Campaign.

Chad, our deepest condolences to all the folks down there, all the family members. I know you're going to be speaking with them. Thanks very much for joining us.

GRIFFIN: Thank you, Wolf.

BLITZER: Coming up, why a former co-worker of the Orlando killer now says he knew something bad was coming. We have new details.